U.S. patent number 4,438,771 [Application Number 06/371,933] was granted by the patent office on 1984-03-27 for passive contactless monitor for detecting cessation of cardiopulmonary.
This patent grant is currently assigned to University of Virginia Alumni Patents Foundation. Invention is credited to Gene D. Block, W. Otto Friesen.
United States Patent |
4,438,771 |
Friesen , et al. |
March 27, 1984 |
**Please see images for:
( Certificate of Correction ) ** |
Passive contactless monitor for detecting cessation of
cardiopulmonary
Abstract
An apparatus and method is disclosed for detecting the cessation
of movement of a body by detecting the voltage produced by the
movement of the charge on said body because of the body's movement.
This is accomplished by a passive contactless conductive pad which
is spaced from the body and in which a potential is induced by the
movement of the body through the movement of the charge on the
body. This potential is amplified and an alarm indication device
responds to the amplified potential to produce an alarm when the
output of the amplifier is below a predetermined value or for a
predetermined period of time. This device enables the unattended
monitoring of breathing and heart functioning for long periods of
time.
Inventors: |
Friesen; W. Otto
(Charlottesville, VA), Block; Gene D. (Charlottesville,
VA) |
Assignee: |
University of Virginia Alumni
Patents Foundation (Charlottesville, VA)
|
Family
ID: |
23466013 |
Appl.
No.: |
06/371,933 |
Filed: |
April 26, 1982 |
Current U.S.
Class: |
600/484;
340/573.1; 600/534 |
Current CPC
Class: |
A61B
5/113 (20130101) |
Current International
Class: |
A61B
5/11 (20060101); A61B 5/113 (20060101); A61B
005/08 (); A61B 005/10 () |
Field of
Search: |
;128/716,721-723,670,671
;340/573 ;128/782,774 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Howell; Kyle L.
Assistant Examiner: Hanley; John C.
Attorney, Agent or Firm: Oblon, Fisher, Spivak, McClelland
& Maier
Claims
What is claimed as new and desired to be secured by Letters Patent
of the United States is:
1. An apparatus for detecting cessation of cardiopulmonary
functioning of a human body, comprising:
a passive conductive means, spaced apart from said body in which a
potential is directly induced by the movement of said body due to
the movement of the charge of said body when said cardiopulmonary
functioning occured;
monitor means responsive to said directly induced potential to
produce a indication of cessation of cardiopulmonary functions of
said body.
2. The apparatus according to claim 1 wherein said monitor means
includes a potential amplification means response to said induced
potential to produce a voltage output representative of movement of
said body and an alarm indication means responsive to the output of
said amplifier means to produce an indication signal by the output
of said amplifier means is below a predetermined value for a
predetermined period of time.
3. An apparatus for detecting cessation of movement of a body
containing a charge comprising:
a passive charge movement detecting conductive means spaced from
said body in which a potential is directly induced on said
conductive means by the movement of said charge caused by the
movement of said body;
potential amplification means responsive to said induced potential
to produce a voltage output representative of movement of said
body; and
alarm indicator means responsive to the output of said
amplification means to produce a signal indicating the cessation of
movement of said body when the output of said amplification means
is below a predetermined value for a predetermined period of
time.
4. The apparatus of claim 1 wherein said passive charge movement
detecting conductive means consists of a pair of conductive layers
separated by an insulating layer and wherein said conductive means
is spaced from said body by at least a covering plastic layer.
5. The apparatus according to claim 1 wherein said passive charge
variation detecting conductive means comprises;
a first conductor; and
a second conductor spaced apart from said first conductor
concentric with said first conductor and with said second conductor
located entirely in the same horizontal plane as said first
conductor.
6. The apparatus according to claim 1 wherein said potential
amplification means responsive to said induced potential has a
variable amplification factor in order to adjust the sensitivity of
said conductive means.
7. An apparatus according to claim 1 wherein said potential
amplification means includes an output display response to said
voltage output to produce a visual indication of body movement.
8. An apparatus according to claim 3 wherein said potential
amplification means and said alarm indication means are constructed
in a same unit and said unit is attached to said conductive means
by leads.
9. A method for detecting cessation of movement of a body
containing a charge, comprising the steps of:
detecting the movement of said body by means of a measurement of a
potential directly produced as a result of said movement of said
charge caused by the movement of said body;
outputting by means of a passive conducting means, said potential
produced by said movement;
amplifying said outputted potential to produce a voltage output
representative of body movement; and
producing an alarm indicating cessation of movement of said body
when said voltage output is below a predetermined value for a
predetermined period of time.
10. The method of claim 9 including the further steps of
encapsulating said conductive means in plastic and placing said
encapsulated conductive means beneath said body to be monitored.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a contactless system for monitoring the
condition of the body or either a human or an animal and providing
an alarm upon detection of a cessation of activity for a
predetermined time.
2. Description of the Prior Art
The field of respiration and heart monitoring has generally been
addressed in the prior art to types of devices which are used in
hospitals and which have a level of sophistication requiring
complex circuitry and a sizable expense. These monitoring devices
have usually taken the form of respiration monitors which are used
mainly in hospitals to signal a nurse when a human patient has
stopped breathing. Among the most prominent of these devices is the
monitoring device which utilizes the connection of electrodes
directly to the skin of a patient in order to sense electrical
resistance changes during respiration in the skin surrounding the
expanding and contracting chest cavity. Quite obviously the
connection of electrodes directly to the patient is not only a
problem with regard to providing satisfactory contact due to
irritation and skin rashes which result from a saline solution
commonly used to provide satisfactory contact but also, this method
provides several problems with regard to maintaining the contact as
the patient moves.
One of the more pertinent problems in recent years has been the
detection of apnea which occurs in infants and is primarily a
cessation of voluntary breathing. This problem has come to be known
as "the sudden infant death syndrome" (SIDS). As is now known in
the medical field, the monitoring and surveillance of infants and
especially infants who have been determined to be high risk during
the critical first six months is seen to save many lives and at
least provide information concerning the cause of this
syndrome.
Quite obviously, the continuous monitoring of an infant for its
first six months of its life is a process which cannot take place
in a hospital because most of the problems with the detection and
the determination of this syndrome is the fact that there are no
warning signs which are given prior to its occurrence. Therefore,
home monitoring is the most useful and most assuring method of
saving lives. The basis of operation for the detection of the
syndrome is the cessation of breathing which can be corrected by
cutaneous stimulation. In other words, once breathing has stopped
and all heart functions have stopped for a period of anywhere from
10 seconds to a minute, the infant's life may still be saved if the
proper technique is used. However, most prior art devices require
an extreme expense on the part of the parents to either rent or
purchase the complicated devices for the home monitoring.
Furthermore, these devices have problems with regard to false
alarms primarily because of proper placement and retention of the
sensor on the child who turns or moves in his sleep.
More recent attempts to solve these problems involve the use of
pressure monitoring devices which rely on a monitoring of the
activity of a child by changes in a pressure transducer located
beneath the child, which changes are induced by the breathing of
the child. These transducer devices such as shown in U.S. Pat. No.
4,033,332 require an active electrical bias for the pad upon which
the infant is resting. In other words, these devices produce a
change in the electrical capacitance in the pad when the child
moves, which change is pressure related, and which change causes a
signal to be developed which can be monitored. When the changes in
the pressure have ceased for a period of time no change in
capacitance is detected and an alarm is registered.
As indicated, these types of pressure monitoring devices require
both an electrical circuit for the pad and for the monitoring of
the output signal from the pad. Thus, not only must the cost of the
device be extremely high but is must also be properly adjusted for
the weight of the child, which changes the capacitance detected,
and for the proper electrical functioning of the two separate
circuits for the pad and for the signal developed from the pad.
Aside from the obvious requirement in the prior art of a separate
power supply for the pad structure which requires a 110 volt
source, there is the associated psychological and convenience
barrier in the mind of the parents who may be apprehensive about
placing something underneath their child or very close to their
child which is plugged into an electrical outlet for long periods
of time. Another inherent disadvantage is that these type of
monitoring systems may not be used in bassinetts or portable
carriers because of their size and the obvious requirement of a 110
volt source.
Lastly, the criticality of the weight factor with regard to the
adjustment of the device would require adjustment of the sensing
device as the weight of the child increases with age, and of course
would be sensitive to other weighted objects in the crib such as
toys, stuffed animals etc.
It is the object of the present invention to provide a passive
contactless monitoring device which overcomes the disadvantages of
the prior art.
SUMMARY OF THE INVENTION
Accordingly, one object of this invention is to provide a novel
monitoring system which is passive in nature, requires no contact
with the body of the person or animal being monitored and which
does not use or require a 110 volt source. This is accomplished
according to the present invention by taking advantage of the
movement of the charge which takes place upon the movement of any
human or animal body which movement of charge induces a potential
in a conductive material.
The device according to the present invention provides for an
apparatus which detects the cessation of movement of a body in
which the body does not contact the apparatus and in which the
apparatus has a passive charge variation conductive pad spaced from
the body which is being monitored and in which a potential is
induced by any movement of the body either from the respiratory
function or the cardiac function. This induced potential is
amplified in order to produce a voltage output which is
representative of movement of the body and in order to give a
signal to an alarm indicator which is responsive to the voltage in
order to produce an indication signal when the output of the
amplifying device is below a predetermined value for a
predetermined period of time.
Another object of the present invention is to provide a thin
construction of the conductive apparatus including alternating
layers of plastic and conductive material which can cover the
entire area underneath or near the body to be monitored regardless
of the weight of the body to be monitored.
A further object of the present invention is to provide a reliable,
inexpensive apparatus which can be used in the home environment and
can be battery operated without the necessity of an attachment to
an electrical outlet and without the necessity of modifying the
environment of the person or infant being monitored with regard to
other objects in the crib or the changing position of an infant
during long periods of unattended monitoring.
A still further object of the invention is to provide a device
sensitive enough to detect motion induced by either the respiratory
function or the cardiac function to provide a double measure of
security and assurance to the parents during long periods of
unattended monitoring.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and many of the
attendant advantages thereof will be readily obtained as the same
becomes better understood by reference to the following detailed
description when considered in connection with the accompanying
drawings wherein:
FIG. 1 is a perspective view of the conductive pad arrangement on a
mattress or bed upon which a infant is shown;
FIG. 2 is a side view of the conductive pad of FIG. 1;
FIG. 3 is a top view of an alternate embodiment of the conductive
pad of the present invention;
FIG. 4 is a side view of the alternate embodiment of the conductive
pad arrangement;
FIG. 5 is a schematic drawing of an exemplary amplifier section of
the present invention;
FIG. 6 is an exemplary schematic diagram of the alarm indicator
section of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, wherein like references numerals
designate identical or corresponding parts throughout the several
views, and more particularly to FIG. 1 thereof, there is shown a
perspective view of the conductive pad arrangement 1 which is
placed on top of a mattress or bed 2. The leads 3 and 4 connect the
conductive pad 1 to the monitoring section 5 which provides the
alarm function as will be described below. Shown upon the pad 1 is
an infant 6 who may be placed at any position on the pad and who
may be of any size, including an adult or animal, regardless of its
weight.
FIG. 2 shows a side view of the conductive pad arrangement 1 which
contains conductive layers A and B enclosed by plastic sheet layers
11, 12 and 13. The length of the conductive pad layers is shown to
be slightly smaller than the length of the plastic layers for
purposes of providing an area where sealing may be accomplished
between the plastic layers to affectively encapsulate the
conductive pads A and B with a plastic layer 12 located
therebetween.
Each human body or animal body contains a net or at least a
accumulation of charge. Thus the infant represented as 6 in FIG. 1
contains a certain amount of charge. When there is movement of a
charge, a potential is induced in a conductive material such as the
conductive pad 1 or 20. Thus the movement of the infant 6 either
through its breathing or its heart beat causes a potential in each
of the layers A and B. Effectively then, the electrode lines 3 and
4 each carry a voltage from the layers B and A respectively which
is fed to a monitor circuit 5. This monitor circuit 5 consists of
an amplification portion shown in FIG. 5 and a alarm indicator
portion shown in FIG. 6. The effect of this monitor device is to
amplify the voltage induced onto the potential electrodes 3 and 4
to provide an indication of movement of the infant 6. The amplifier
and the alarm indicator circuit as constructed and discussed below,
is set up in such a manner that an alarm is indicated when a
potential is not induced on the lines 3 and 4 for a predetermined
period of time.
That is, the alarm functions when the body 6 has not either had a
heart beat or a resipatory function within a predetermined period
of time. This provides an alarm indication to, for example the
parents, to start the artificial respiratory procedures necessary
to induce the continued rhythmatic breathing.
An alternate embodiment for the construction of the pad and the pad
layers is shown in FIGS. 3 and 4 wherein the pad 20 has a side by
side construction for the layers A' and B' with an air space
located between. The central rectangular pad A' is surrounded by a
central rectangular spacing labeled 24 which in turn is surrounded
by the conductive layer B'. Each of the layers A' and B' and the
space 24 is enclosed by top and bottom plastic layers 21 and 22
respectively. The lead connections 3 and 4 shown in FIG. 1 is
equally applied to the structure of FIGS. 3 and 4 with each of the
leads 3 and 4 being respectively connected to the layers B' and
A'.
The amplifier portion shown in FIG. 5 consists of three stages of
amplification including the respective three operational amplifiers
IC1, IC2 and IC3. The conductors A and B or A' and B' are connected
to the input of the first amplification stage through resistors R2
and R1 respectively. Each of the operational amplifiers are
constructed of a CMOS operational amplifier with a very high input
impedance. The normal feedback operation for the amplifier section
is shown by the resistance R3. The purpose of resistor R1 is to
slowly discharge the plate attached thereto so that only movements
of charged objects but not stationary objects are detected. Because
all physical bodies bear a net charge, movement near the sensor
plate will induce potential changes on both plates so that the
first amplification stage actually amplifies the difference between
the potentials of the two plates. The difference in resistance
between R1 and R2 provides a difference between the two voltages
which is then amplified. The potentiometer R4 allows the overall
amplification to be varied by a factor of 10. The capacitors C1-C4
are components of a band pass filter which eliminates undesirable
low frequency and high frequency noises. By choosing appropriate
values for the capacitors C1-C4 of the band pass filters, either
heart beat, breathing movements or both heart beat and breathing
movements can be detected. This apparatus is sensitive enough to
detect the breathing movements of small infants, even when the
sensor plate is placed below the mattress pad. The device has been
tested to function successfully with infants weighing as little as
6 pounds.
The output of the amplifier section and most particularly, the
amplifier IC3 is connected to the input of an edge-triggered
retriggerable one-shot, IC4. The pulse duration of the one-shot is
set with R10 and C5 to 20 seconds. Thus if any large amplitude
voltage swing occurs at the amplifier output at intervals of less
than 20 seconds the Q output of the one-shot will remain low. If no
such fluctuations occur for more than 20 seconds, the Q will go
high and, via buffer IC5, drive the buzzer as shown. The 20 seconds
is adjustable by means of the above-mentioned R10 and C5.
Other monitoring features are possible with the present invention
such as a light which would indicate by a flashing with each output
of the amplifier to indicate either a breathing or a heart action.
This can occur through the use of the diode D1 and the resistor R9
shown in FIG. 5 at the output of the amplifier circuitry.
The remaining circuitry, including the diode D2 and the resistors
R11, provide the necessary connections for the one-shot operation.
Likewise, any other amplifier device which can amplify the
potential on the electrodes 3 and 4 of FIG. 1 may be used in order
to drive the alarm indicator means and certainly other alarm
circuitry, known to those skilled in the art, may be used to
provide the necessary indications of cessation of breathing or
cardiac movement.
The conductive layer used in the above embodiment employed aluminum
foil, however, other workable conductive layers can be constructed
of copper wire mesh, conductive plastic and the like.
The following lists of resistor and capacitor values indicate the
example shown and described above with respect to FIGS. 5 and 6 and
are not meant to be limiting. Resistors R1, 20M; R2, 1M; R3, 20M;
R4, 100K (pot); R5, 10K; R6, 1; R7, 10K; R8, 1M; R9, 1K; R10, 100K;
R11, 330K; Cl, 100 .mu.F; C2, 0.1 .mu.F; C3, 100 .mu.F; C4, 0.1
.mu.F; C5, 100 .mu.F.
The amplifier sections consisting of operational amplifiers IC1,
IC2 and IC3 consists of 1/2 of a 353 CMOS chip, with the diode D1
being a light emitting diode (LED) and the diode D2 being a
IN4148.
The above describe monitoring device presents a passive contactless
system which can be easily constructed and inexpensively made to
enable, for example, parents to purchase these devices for home use
during the first several critical months of an infant's life,
either as a routine cautionary procedure or as instructed by a
physician in the instances where the SIDS is most likely to occur.
This is particularly important with infants who have had previous
occurrences of this syndrome or for parents have had other children
who have died in this manner.
The reliability and moderate costs of this device provides a
significant area of improvement in the monitoring, at home, of
infants through the first several critical months of their
life.
The passive pad i.e., requiring no active electrical source,
permits the entire circuits to be battery operated without a need
for a 110 volt source and without the need to place a baby on a pad
which is attached to a voltage source for long periods of time.
Obviously, numerous modifications and variations of the present
invention are possible in light of the above teachings,
particularly with regard to the construction of the amplifier and
alarm circuitry. It is therefore to be understood that within the
scope of the appended claims, the invention may be practiced
otherwise than as specifically described herein.
* * * * *